Two-needle pneumatic disengaging mechanism

ABSTRACT

A pneumatically actuated needle bar mechanism for use in a twoneedle sewing machine of the vertical hook lockstitch type is disclosed. The pneumatically actuated needle bar mechanism selectively controls the position of either or both needles and positively locks either or both needles in either the sewing (engaged) position or the non-sewing (disengaged) position. The mechanism is controlled by pedal operated remote pneumatic valves.

United States Patent 1191 Boser Oct. 21, 1975 [S4] TWO-NEEDLE PNEUMATIC DISENGAGING 3,077,846 2/1963 Bono 112/221 MECHANISM 3,266,449 8/1966 Berg et a1. 112/221 Inventor: Ronald J. Boser, Dix H1118, N.Y. FOREIGN PATENTS 0R APPLICATIONS A signeez Specia Se g Systems, Inc, New 661111311} York, NY. Primary ExaminerGeorge H. Krizmamch [22] Flled: Dec. 12, 1974 [21] Appl. No.: 531,947 [57] ABSTRACT A pneumatically actuated needle bar mechanism for 152 US. Cl. 112/221; 112/219 B use in a two-needle Sewing machine of the vertical [51 1111. C1 D058 69/08 hook lockstitch yp is disclosed The pneumatically Fi l (Search 122 220 221 2 9 B 3 actuated needle bar mechanism selectively controls [56] References Cited UNITED STATES PATENTS 669,972 3/1901 Anderson 112/219 B 2,868,152 l/1959 Benink et al 112/221 lIll 122/164, DIG. 3

the position of either or both needles and positively locks either or both needles in either the sewing (engaged) position or the non-sewing (disengaged) position. The mechanism is controlled by pedal operated remote pneumatic valves.

6 Claims, 13 Drawing Figures 1 160 A I72. EXHAUST 1 EXHAUST I681 i [54. 1 170 154 [7'6 ,1 1 y l i 114 I84 e n 1 1a;

'- 1 AR 1 a l} 2, SUPPLY s I I 18 156 I7 168 130 5 LEFT FOUR WAY IGGRIGHT FOUR WAY 182 M L6H;

U..S. Patent Oct. 21, 1975 Sheet10f7 3,913,508

US. Patent Oct. 21, 1975 Sheet4 of7 3,913,508

FIG.6A.

5 I l b 6 F m m K I! k U.S. Patent Oct.21,1975 Sheet50f7 3,913,508

FIG]

EXHAUST EXHAUS SUPPLY I8 156 178 153' I I80 I I 8 I80 f W IGGRIGHT FOUR WAY I82 VALVE U.. Patent Oct. 21, 1975 Sheet 6 of7 3,913,508

LEFT PEDAL US. Patent Oct. 21, 1975 Sheet7of7 3,913,508

RIGHT PEDAL a wire stay or slide fastener.

TWO-NEEDLE PNEUMATIC DISENGAGING MECHANISM SUBJECT MATTER OF THE INVENTION The present invention relates to an improved mechanism for selectively disengaging either or both needles of a two-needle industrial sewing machine.

BACKGROUND OF THE INVENTION Sewing machines designed for industrial operations I frequently include two needles to enable the operator to sew two parallel seams in a single operation. Twoneedle machines of the vertical hook lockstitch type as shown, for example, in the Quist U.S. Pat. No. 2,329,484 and the 'Attwood et a1. U.S. Pat. .No. 2,765,759 are well adapted for this purpose. When using such a machine for sewing parallel seams it is deor to avoid an impenetrable portion 'of 'the work such The art has developed various mechanisms for raising or disengaging the needles of a two-needle sewing machine. Thus, in Basso U.S. Pat. No. 1,899,303 there is .provided a single needle supporting bar fitted with -a head having separate slide ways for each of the two needle holders. The needle holders are provided with spring-loaded detents to lock the holders in either the engaged ordisengaged position. Similar manually oper ated needle positioning devices are shown in Kufall U.S. Pat. No. 2,495,586, Weigert U.S. Pat. No. 3,763,805 and Shuffield U.S. Pat. No. 3,763,806. While each of the above patents provides a mechanism whereby either or both needles of a two-needle ma- No. 3,545,390. In these patents two separate needle bars are provided together with a mechanical disengaging means by which either needle bar alone may be disengaged. While the operating levers for these mechanisms have been removed from the needle holder, it is still necessary for the operator manually to move a lever to control the device. These mechanisms are both more complex than those shown in the Basso and Kufall patents and introduce two additional disadvantages into the machine. First, the use of two separate needle bars, in the context of those machines, places a limitation on the proximity of the needles, and, hence, limits the minimum spacing of the parallel seams to be sewn. Second, the mechanism is not capable of disengaging both needles simultaneously. These specific disadvantages have been overcome in the mechanisms of the separate mechanically operated disengaging means for each needle bar. However, these mechanical mechanisms must still be manually operated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved mechanism to selectively control the position of either or both needles of a two-needle sewing machine. While the present invention will be described in connection with a vertical hook lockstitch sewing machine, it may also be utilized on other types of twoneedle sewing machines. Another. object of the.invention is to provide a positively operating, remotely controlled needle engaging mechanism. A further object of the invention is to provide a pneumatically actuated mechanism which is capable of rapid response to a remote signal and functions to lock the needle in either axial extension of each slidable needle-bar. Each needle sirable that eitheror both of the needles be capable of ,being raised to a nonoperating or disengaged position i to enable the operator toturn left or right seam comers bar actuating cylinder communicates through pneumatic ducts with remotely positioned four-way valves which are actuated by treadles or other means to either of two extreme positions. Actuation of the treadle controls the four-way valve to direct pneumatic pressure into one side of the double acting pneumatic cylinder,

so as to drive a piston connected to the needle bar into a locked position constituting either an operating (i.e., engaged) position or a nonoperating (i.e., disengaged) position.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects of the invention will be more clearly understood when considered in connection with the detailed description and the accompanying drawings in which 7 FIG. 1 is a front elevational view, partly in section, of a two-needle sewing machine incorporating thepneumatic needle disengaging mechanism according to the present invention. I

FIG. 2 is an elevation view of the left end of the sewing machine as viewed in FIG. 1 with the head cover removed and part of the spacer cut away.

FIG. 3 is an enlarged vertical'section of the needle bar assembly taken along line 3-3 of FIG. 2.

FIGS. 4A and 4B are, respectively, rear and left side views of the detent bar of the needle bar assembly.

FIG. 5 is an exploded view of the parts associated with the right needle bar shown in FIG. 3.

FIGS. 6A and 6B are, respectively, rear and right side views of the retractable needle holder associated with the right needle bar shown in FIG. 3.

FIG. 7 is a fragmentary cross-sectionalview of the pneumatic system including the double acting pneumatic cylinders for the left and right needle bars, the left and right two-position four-way valves and the air supply and showing the left needle in the retracted or disengaged position while the right needle is in the unretracted or engaged position.

FIG. 8A-is a plan view of the left pedal assembly, partly in section, and showing the pedal in a position to retract the leftneedle. v

FIG. 8B is a sectional view of the left pedal assembly taken along the line 8B-8B of FIG. 8A.

FIG. 9A is a plan view of the right pedal assembly, partly insection, and showing the pedal in a position to engage the right needle. V

FIG. 9B is a sectional view of the right pedal assembly taken along the line 93-98 of FIG. 9A.

filed Oct:- 2, 1973.

'DETAILEDTDESCRIPTION or THE PREFERRED I EMBODIMENT OF THE INVENTION Referring first to FIGS. 1 and, 2-, the sewing-machine main frame in which thepresent invention may be incorporated isindicated generally'at l and. comprises a work'supporting base portion 12, a vertical standard 14 and an overhanging arm 16 with a needle head 18 at its, free end. A rotatable shaft 20 extending longitudinally, within the overhanging arrn l6 and suitably journaled therein extends through the right wall of the vertical standard 14 and carries on itsright end (as viewed in FIG. 1} acombination hand wheel and pulley 22 and an electromechanical synchronization unit 24. A belt (not shown.) from an electrodrive (not shown) drives the pulley 22 and the rotatable shaft 20. The electromechanical synchronization unit 24 supplies electrical signals to the electrod rive to cause the machine to stop with the needle bars in the up or down position as may be desired by the operator. "The synchronization unit may also con'trol the trimming of the thread'at the "beginning or at the end of a garment stitching operation; The synchronization "unit 24 here contemplated may; for example, be a QuickModel No. 800-ST-362 unit or an Amc'o' Model No.*800-XT-362 unit.

The rotatable shaft 20 extends from the pulley 22 frame-$8 pivoted at its upper end on pine 40. As set forth below,- meanstare, provided to rock the frame 38 in the direction of the feed, i.e., in the line of stitchformation, to impart a needle feed action to the work. This rocking motion is derived from apin 42 attached to the frame 38 and providing va pivotal attachment for one end; of a rocker line. 44, the other end of which is-pivotally connected with arm 46 which extends downwardly and outwardly from collar 48 secured to a hollow rock shaft ,7 I I I I The lower endof the right needle bar 36 is fastened to a needle bar clamp 52 by a dog screw 54. In similar manner the lowerend of the left needle bar 56 isfas- 'tened to the needlebar clamp 52 by a dog screw 58 (see FIG. 3). As'the left and right needle bars 56 and 36, respectively, are thus clamped together, both will reciprocate when the right needle bar 36 is driven with a reciprocating motion as set forth above.

' "As shown most clearly in FIGSi 3 and -,'both needle I bars 36 and 56 are hollow and both contain identical parts. For this reason, the right needle bar assembly only 'will be described in detail and the corresponding parts of the left needle bar assemblyidentified by primed numbers. A similar practice will be followed with respect to the left and right pedal assemblies (FIGS. 8 and 9) and the pneumatic control system (FIG; 7). The needle bar-mechanism used inthe present invention is also shown in my copending application 'Ser. No. 402,876 entitled Sewing Apparatus Referring now principally to FIGS. 3 and-5, air hose 60 communicates with the top of the needle bar 36 by means of .a hollowthreaded nut 62 which .isrthreaded into the needle bar-andan air collar 64. Air hose 60 communicates with theair collar-64 through a radial hole 66 formed in the collar 64 and the fitting 68 soldered into the collar 64. Air collar 64 is fastened to the top of the needle bar 36'by a screw 70 provided with an axial bore 72 which communicates with a radial bore 74. Screw 70 is threaded into the hollow nut 62 with its radial bore 74 aligned with the radial hole 66 of the air collar 64 to provide an air passage communicating'between the air. hose 60 and the interior portion of the needlenbar 36. In a similar manner,-air hose 76 (FIG..7) is connected to the needle bar 36 by an air inlet collar 78 through an aligned radial hole formed in the collar and a radial hole 80 formed in the needle bar 36. Air hose 76 communicates with the needle bar at a point just above the dividing seal portion 82 of the needle bar. v p

An air piston 84 is slidably mounted within the needle bar 36 between the air intake points corresponding to air hoses 60 and 76 and is fastened to piston rod 86 by a nut 88. A cup seal 90'is positioned around the piston rod 86 and within the needle bar 36 so as to form a lower pressure chamber within the needle bar 36 and bounded at the ends by piston 84 and cup seal 90. Thus the' air piston 84 forms the movable element in a double acting pneumatic cylinder and will be driven downming surfaces'94 and 96 adapted to selectively engage movablelocking balls 98, 100. Locking balls 98, 100 are slidably mounted within a retractable needle holder 102 (see FIGS. 6A and 6B) which, in turn, is slidable within a vertical slot 104 formed in the needle bar 36.

A'detent bar 106 (see FIGS. 4A and 4B) is secured to the lower end of needle bar 36 by do'g screw 54. Similarly, detent bar 106' is secured to the lower end of needle bar -'56 by dog screw58. I

As shown in FIGS. 5, 6A ,and 6B, the retractable needle holder l02-has .a cylindrical upper section 108 that has been longitudinally sectioned off to form a flat portion ll0'and a plate-like lower section 112. A vertical slot 114 extends-from the flat into the cylindrical section 108 and down into the plate-like lower section 112. Two horizontal holes 116, 118 having diameters larger than the width of the vertical slot 114 are bored from the flat 110 into the cylindricalsection 108 with the slot 114bisecting the holes. The upper and lower aneedle 122 while a horizontal hole 124 serves as a needle stop. The needle 122 is locked into position by a set screw 126 threadedinto the horizontal locking 4 hole 128. I

The cam member 92 (FIGS. 3 and 5) is formed with flat sides so as to slide within the vertical slot 114 of the retractable needle holder 102. Lower camming surface 96 of the cam member 92 is adapted to contact locking ball 100 and urge said locking ball outwardly from the needle holder 102 along hole 118 when the piston 84 is driven downwardly within the needle bar 36. Similarly, the upper camming surface 94 ,is adapted to ball outwardly from .the needle holder 102 along hole 116 when the piston 84 is driven upwardly within the needle bar 36. i l

The detent bar106 (FIGS. 4A, 4B and 5) includes as its upper section the dividing seal portion 82. The central section 130 of the detent bar is sectioned longitudinally from a cylinder to form a flat 132 which mates with the flat 110 of the retractable needle holder 102. Two shallow holes 134, 136 are formed in the flat 132. The shallow holes 1 34 and 136 are smaller in diameter than the locking balls98, 100 so as to allow a portion of said balls to protrude from the retractable needle holder 102 into the detent bar 106 when aligned respectively with the upper or lower horizontal holes 1 16, 118. The lower section 138 of the detent bar 106 is cylindrical in shape and has formed therein a slot 140 to receive the plate-like section 112 of the retractable needle holder 102. Two holes 142, 144 are formed in the cylindrical section 138 of the detent bar 106. The upper hole 142 is aligned to receive the top of the dog screw 54 and thereby secure the detent bar 106 to the needle bar 36 while the lower hole 144 is provided for access to theneedle set screw 126. Horizontal circular groove 146 is aligned with the needle stop hole 124 in the retractable needle holder 102 when the needle holder is in the operating or unretracted position to permitiobservation of the position of the needle 122 within the needle holder.

A small horizontal hole 148 is formed in the lower portion of the needle bar clamp 52 perpendicular to the plane of the needle bars 36 and 56 and midway between the axes of the needle bars to receive a roll pin 150. The roll pin 150 is adapted to abut against and support the adjacent needle holder 102 or 102 so as to prevent the lateral deflection of either needle holder 102 or 102' when the other needle holder is in the re tracted position. Thus, as shown in FIG. 3, the roll pin 150 prevents a lateral deflection of the needle holder 102 in a leftward direction when needle holder 102 is in its retracted position. Horizontal holes 152, 152' in the needle bar claim 52 are formed in alignment with circular groove 146 of the detent bar 106 to permit observation that the needles 122 are properly seated while horizontal holes 154, 154 are aligned with holes 144, 144 of the detent bar 106, 106' to provide access to the needle set screws 126, 126.

FIG. 7 illustrates in diagrammatic form the pneumatic supply and control system for the needle bar actuating mechanism of the present invention. Air from an air supply source 156 enters a tee connector 158 and is divided between two air supply tubes 160, 160. The air supply tube 160 communicates with the right four-way valve 162. Valve 162 comprises a cylindrical body 164 and an axially disposed spool 166. The valve body contains five air ports including a central air supply port 168 which'communicates with the air supply tube 160, two outlet pressure ports 170, 172 which communicate, respectively, with the air 'hoses 60 and 76 and two exhaust ports 174, 176 positionedoutwardly from the outlet pressure ports 170, 172. The spool 166 of the valve 162 comprisesa central rod 178 and three piston portions 180 and actuating headsl82, 183 affixed at each end of the central rod '178. As shown in FIG. 7, a spring 184 urges the spool 166 into a left operating position within the valve body 164 whereby ports 168 and 170 are in communication and ports 172 and 176 are in communication. Under these circumstances, pressurized air from the air supply 156 is directed through the air supply tube 160, through the valve body 164 and air hole 60 into the upper portion of the needle bar 36 whereby the piston 84, the piston rod 86, the cam member 92 and the needle holder 102 Y are driven downwardly within the needle bar 36. As the cam member 92 moves downwardly, the camming surface 96 urges locking ball outwardly against the flat 132 of the detent bar 106. When the locking ball 100 becomes aligned with the shallow hole 136 in the detent bar 106, the cam surface 96 will urge the ball partially into the shallow hole 136 whereby the needle holder 102 will be locked in the engaged or sewing position.

When the spool 166' has been moved to the right within valve body 164' so as to compress the return spring 184' as shown in FIG. 7, air from the air supply 156 is directed through air supply tube air supply port 168', outlet pressure port 172' and air hose 76' into the left needle bar 56 below the air piston 84'. Air pressure acting on the lower side of the air piston 84' drives the piston upwardly in the needle bar assembly and carries with it piston rod 86', the cam member 92 and the needle holder 102. 'Asthe cam member 92' moves upwardly, the camming surface 94 urges locking ball 98 upwardly and outwardly against the flat 132' of the detent bar 106'. When the locking ball 98' becomes aligned with the shallow hole 134' in the detent bar 106', the cam surface 94' will urge the ball partially into the shallow hole 134' whereby the needle holder 102' will be locked in the disengaged or nonsewing position.

It will be appreciated that when the spool 166 of the right four-way valve is in the left position as shown in FIG. 7 so as to admit air under pressure into the upper portion of the right needle bar 36, the portion of the needle bar 36 below the piston 84 communicates to the atmosphere through air hose 76, pressure port 172 and exhaust port 176. Similarly, when the spool 166' is in the right position as shown in FIG. 7 so as to admit air under pressure into the lower portion of the left needle bar 56, the portion of thejneedle bar 56 above the piston 84 communicates to the atmosphere through air hose 60', pressure port and exhause port 174.

Use of the pneumatic systemas shown diagrammatically in FIG. 7 permits both needles of a double needle sewing machine to be moved to either an operating or a nonoperating position by means of remotely located four-way valves. The valves are provided with compression springs 184, 184 arranged normally to cause both needles to be in the operating'or sewing position.

In order to provide for maximum efficiency and convenience, the four-way pneumatic control valves 162 and 162' may be incorporated into pedal assemblies or treadles as'shown in FIGS. 8A, 88, 9A and 9B. The pedal assemblies conveniently may be permanently affixed to the sewing machine stand (not shown).

As shown in FIGS. 9A and 9B, the right pedal assembly comprises a box 186 having a bottom portion 188, left and right side portions 190, 192, a front portion 194 and a rear portion 196. A pipe support flange 198 is secured to the bottom portion 188 by two screws 200. Pipe support flange 198 is appropriately formed to engage treadle pipe 202 which forms a portion of the 186 by screws 212. Air hoses 60, 76 and 160 are secured to the bottom portion 188 by a claim 214 and lock screw 216 and exit from'the pedal box 186 through a grommet 218 mounted in the rear portion side portions 190, 192. The pedal 220 and shaft 222 are held in position' by retaining rings 224. A screw 226 is adjustably secured to the right edge of the pedal 220 and locked into position by lock nut 228. The screw 226 is located so that when the pedal is positioned as "shown by the solid lines in FIG. 9B, screw 226 will be aligned with the axis of the spool 166 of the four-way valve 162. Screw 226 is then adjusted so that it contacts the adjacent spool actuating head 182 and drives the U 196. Pedal 220 pivots on a shaft 222 mounted in the to-drive said needle into its second disengaged position.

spool 166 into its left operating position. In similar manner, a screw 230 is adjustably secured to the left .edge of the pedal 220 and locked into position by a lock nut232. Screw 230 is located so that when the pedal 220 is positioned as shown by the broken lines in FIG. 9B, screw 230 will be aligned with the axis of the spool 166 of the fourway valve 162. Screw 230 is then adjusted so that it contacts the adjacent spool actuating head 183 and drives the spool 166 into its right operatmg position. In FIGS. 8A and 8B the left pedal assembly is shown with the pedal 220 depressed so that the adjustable screw 230' contacts the spool actuater 183 and drives the spool 166 of the fourway valve 162' into the right operating position.

Referring to FIGS. 3, 7, 8A, 8B, 9A and 93, it will be appreciated that when the pedal 220 or 220' is in the position shown in.FIG.-9B, i.e., the pedalis not depressed, the corresponding holder 102 or 102 and the associated needlel22 or 122 will be in the operating or sewing position. However, when the pedal 220 or 220' is in the position shown in FIG. 8B, i.e., the pedal is depressed, the corresponding needle holder 102 or 102 and associated needle 122 or 122' will be in the retracted or nonoperating position.

The mechanism herein provided enables the operator quickly and positively to actuate either or both needles to the desired position without removing the operators hands from the work. This is particularly advantageous where parallel seaming operations are being performed on garments such as coat lapels or shirt collars or pockets where it is desirable not to have the lines of stitching cross and where either or both right-hand and left-hand corners are involved. When it is necessary for a parallel seam to cross cording, a stay, a wire or a fastener, it may be necessary to retract both needles either simultaneously or sequentially and to reengage the needles either in the same or another sequence.

While the invention has been described in connection with specific illustrative embodiments .thereof and in specific uses, it should be understood that it is not limited thereto since obvious modifications thereof will occur to those skilled in. the art without parting from the spirit and scope 'of the invention as set forth in the appended claims.

What is claimed is:

1. In a-sewing machine designed to sewlstitches in parallel spaced lines, the appratusc'omprising a pair of .needle bar means'each including a needle bar and a needle for forming stitches from a respective thread, means actuated pneumatically within each of said needle bars and connected'with said needle and adapted to move said needle axially with respect to said needle bar between a first engaged position and a second disengaged position, a source of pressurized air, and a pair of valve means in communication with said source of pressurized air and said pneumatically actuated means, each-of said valve means operable between first and second positions to direct air under pressure into said pneumatically actuated means, said valve means in its said firstposition adapted to direct air'under pressure into said pneumatically actuated means so as to drive saidneedle into its first engaged position, said valve means in its second position adapted to direct air under pressure'into said pneumatically actuated means so as V '2. The apparatus of claim 1 including: ameans associatedwith each of said valve means to position said valve means in either of saidfirst or second positions.

retain said needle in one of said first or second positions.

4. In a sewing machine designed to sew stitches in parallel spaced lines, the apparatus comprising a pairof needle bar means each including a needle bar and a needle for forming stitches from a respective thread. means actuated pneumatically within each of said needle bars including movable piston means connected with said needle and adapted to move said needle axially with respect to said needle bar between a first engaged position and a second disengaged position, camming means connected to said piston means for reciprocating motion therewith in a first axial direction. upper and lower locking means driveably cooperating with said camming means, needle holder means driveably connected to said camming means through said locking means for reciprocating motion in said first direction, said locking means arranged, for sliding motion relative to said needle holder means in a second direction transverse to said first direction under the influence of said camming means, detent means'fixed to said needle bar means including upper and lower locking recesses adaptedto engage, respectively, said upper and lower locking means, said lower recess defining a first engaged position of saidineedle and said upper recess defining a second disengaged position of said needle, a source of pressurized air, and a pair of valve means in communication with said source of pressurized air and said pneumatically actuated means. each of said valve means operable between first and second positions to direct air under pressure into said pneumatically actuated means, said valve means in its said first position adapted to direct air under pressure into said pneumatically actuated means so as to drive said needle into its first engaged position wherein said lower locking means is engaged with said lower recess of said detent means, said valve means in its second position adapted todirectair under pressure into said pneuniatically actuated means. so as to drive said needle intoits second disengaged position wherein said upper locking 9 10 means is engaged with said upper recess of said detent 6. The apparatus of claim 4 including: oscillatable means. pedal means drivingly engaged with each of said valve 5. The apparatus of claim 4 including: means associmeans to position said valve means in either of said first ated with each of said valve means to position said or second positions. valve means in either of said first or second positions. 5 

1. In a sewing machine designed to sew stitches in parallel spaced lines, the appratus comprising a pair of needle bar means each including a needle bar and a needle for forming stitches from a respective thread, means actuated pneumatically within each of said needle bars and connected with said needle and adapted to move said needle axially with respect to said needle bar between a first engaged position and a second disengaged position, a source of pressurized air, and a pair of valve means in communication with said source of pressurized air and said pneumatically actuated means, each of said valve means operable between first and second positions to direct air under pressure into said pneumatically actuated means, said valve means in its said first position adapted to direct air under pressure into said pneumatically actuated means so as to drive said needle into its first engaged position, said valve means in its second position adapted to direct air under pressure into said pneumatically actuated means so as to drive said needle into its second disengaged position.
 2. The apparatus of claim 1 including: a means associated with each of said valve means to position said valve means in either of said first or second positions.
 3. The apparatus of claim 1 including: a locking means within each of said needle bar means adapted to retain said needle in one of said first or second positions.
 4. In a sewing machine designed to sew stitches in parallel spaced lines, the apparatus comprising a pair of needle bar means each including a needle bar and a needle for forming stitches from a respective thread, means actuated pneumatically within each of said needle bars including movable piston means connected with said needle and adapted to move said needle axially with respect to said needle bar between a first engaged position and a second disengaged position, camming means connected to said piston means for reciprocating motion therewith in a first axial direction, upper and lower locking means driveably cooperating with said camming means, needle holder means driveably connected to said camming means through said locking means for reciprocating motion in said first direction, said locking means arranged for sliding motion relative to said needle holder means in a second direction transverse to said first direction under the influence of said camming means, detent means fixed to said needle bar means including upper and lower locking recesses adapted to engage, respectively, said upper and lower locking means, said lower recess defining a first engaged position of said needle and said upper recess defining a second disengaged position of said needle, a source of pressurized air, and a pair of valve means in communication with said source of pressurized air and said pneumatically actuated means, each of said valve means operable between first and second positions to direct air under pressure into said pneumatically actuated means, said valve means in its said first position adapted to direct air under pressure into said pneumatically actuated means so as to drive said needle into its first engaged position wherein said lower locking means is engaged with said lower recess of said detent means, said valve means in its second position adapted to direct air under pressure into said pneumatically actuated means so as to drive said needle into its second disengaged position wherein said upper locking means is engaged with said upper recess of said detent means.
 5. The apparatus of claim 4 including: means associated with each of said valve means to position said valve means in either of said first or second positions.
 6. The apparatus of claim 4 including: oscillatable pedal means drivingly engaged with each of said valve means to position said valve means in either of said first or second positions. 